Variables that influence the relationship between oviposition preference and offspring performance in a leafmining beetle

The relationship between oviposition and offspring performance in Brachys tessellatus (F), a leafmining beetle, was investigated in field and laboratory studies from 1991-1995. For many insects whose larval development is confined to a leaf or stem of plants, such as leafminers and gallmakers, it is thought that the influence of maternal oviposition choice is critical for offspring success. This study examines this hypothesis and explored the variables that might influence this relationship.; An oviposition preference hierarchy reveals the choices a female makes when a preferred host is not available and one hypothesis is that the strength of a preference for a given host should correspond with the larval performance on that host. I found that B. tessellatus does have a preference hierarchy and that it varies between field and laboratory, suggesting that environmental factors influence host use and preference. I suggest that host availability and adult habitat preference affect host use in the field.; The correspondence of preference to performance was tested in the field and the results indicate that there are no significant differences in early larval performance (egg survivorship and mine initiation by first instars) among the five oak species (Quercus spp.). However, larval survivorship to the pupal stage was restricted to two species, Q. laevis (turkey oak) and Q. marylandica (blackjack oak). Overall, the influence of host choice on larval performance seems muted when contrasted with the impact that natural enemies have on larval success.; One hypothesis for variation in host preference and subsequent larval performance is that host use experience may influence preference. I tested this hypothesis using two populations of beetles with very different host use experience and found that the population who was restricted to one host species in its habitat exhibited no difference in preference for either blackjack oak or turkey oak. The other population showed a significant preference for it over turkey oak. This is attributed to host availability and host use experience.; Oak species exhibit considerable variation in their phenology, which has significant implications for insects whose own phenology may be synchronized with these hosts in order to successfully exploit the resources. The beetles have a long period of oviposition during the growing season, and subsequently, the larvae are often at different stages of development at the end of the growing season. I tested the hypothesis that (early) leaf abscission phenology impacts the beetles by reducing their larval development time, and subsequently it can either kill them or reduce subsequent pupal weights. My results reveal that early abscissed cohorts of beetles had significantly lower pupal weights (means were 20% lower between first and last abscised cohorts). Field and lab- maintained populations of beetles were found to show a significant and positive correlation between body size and one measure of fecundity, daily oviposition rate. I found a lack of an overall pattern of increasing beetle survivorship with later dates of leaf abscission, which coupled with increased pupal weights, suggests that the beetles has adapted to the variation in leaf abscission phenology via developmental plasticity that permits successful completion of larval development over a range of development times. (Abstract shortened by UMI.)...